In this study, SAC mostly happened in the spring and the autumn,but seldom in the winter.
The SPT results showed that SAC and PAC patients more frequently and severely displayed allergic reactions to dust mite allergens and mites maybe the most common allergen in children with allergic conjunctivitis. Because dust mites like warm and wet weather, so dust mites bred more in the spring and autumn than in the winter.
No correlation was found between the ocular symptom/sign scores and the SPT grades in response to dust mite allergens. But we found significantly positive correlations between ocular symptom/sign scores and disease duration. The longer the disease lasted, the higher the patients’ symptom or sign scores. Lasting moderate or severe allergic reaction to dust mite allergens may be responsible for the ocular symptoms and signs. Therefore, to avoid treatment difficulty and the aggravation of symptoms and signs caused by the delay in diagnosis, timely antiallergic treatment is recommended.
The results showed that the number of children in the case group who had ever been exclusively breastfed was lower than in the control group. The mean duration of exclusive breastfeeding in the case group was shorter than in the control group. These results indicated an association between a history of breastfeeding with a lower rate of allergic eye diseases.We speculate that exclusive breastfeeding may play an important protective role in the AC.As reported by Kull et al. that breastfeeding for four months or more could reduce the risk of eczema and onset of the allergy. In addition, we found that parental allergy history in the case group was significantly higher than in the control group. Allergic rhinitis was most common among their parents. Therefore, prolonged breastfeeding could be a particularly recommended way for infants to reduce the risk of onset of AC, especially with a parental allergy history.
Systemic allergic diseases were closely related with AC. According to our study, allergic rhinitis was the most common, followed by eczema, asthma and urticaria papulosa. Investigatingthe systemic allergic history was necessary in the clinic, especially for children without typical symptoms and signs or children were too young to express themselves. This would help with diagnosis and provide appropriate treatment.
Interestingly, children with ATH were more common in the case group, which suggested thatallergic conjunctivitis may be related to ATH, a result consistent with previous researches [16–18].The conjunctiva are located in the upper extremity of the respiratory system, and the nasolacrimal duct is a drainage system into the nose . Allergens and allergic mediators drain to the nose by this pathway, generating nasal symptoms. The conjunctiva and the nose make up an entire system [1, 2, 5–8]. This can also be explained, allergic rhinitis and conjunctivitis were always co-existent and persistent to repeatedly happen. SAC and PAC were considered to be associated with type I hypersensitivity reactions. Xiaowen Zhang et al. found that the rate of IgE presenting in the adenoids or tonsils was significantly higher than in the serum of childhood ATH, which suggests a role for local atopy [21, 22]. Allergy control may play a role in reducing the rate of adenotonsillectomy in children suffering from allergic reactions caused by ATH . We assumed that in children suffering from PAC combined with ATH, effective PAC control could alleviate the ATH symptoms. Children with ATH would be suggested to have an ophthalmic exam to determine if they are suffering from AC, in order to give more suitable synchronous treatments.
The ocular surface inflammation was usually driven by mast cells, which led to rubbing eyes, itching, blinking and redness in the acute phase .The symptoms of SAC and PAC in children were typical, mainly including eye rubbing, itching, blinking and redness. Nearly half the children experienced these symptoms. The top three clinical signs of AC were chemosis, tarsal conjunctival papillary hypertrophy, and bulbar conjunctival hyperaemia, but they were not specific. Discoloration, limbal hypertrophy, mucus secretions and keratitis were the characteristic signs. Discoloration and limbal hypertrophy always occurred and could make the eye circumference become thickened and opaque. Keratitis and mucus secretions were rare and often happened when eye rubbing was uncontrollable.As children are different from adults, they were not be able to express their feelings accurately and have a variety of clinical manifestations. We always have difficulties in clinical diagnosis, so the more we learn about the characteristics of symptoms and signs of SAC and PAC in children, the more professional the decisions we will make concerning diagnosis and treatment.
This study also had some limitations. First, the sample of subjects in this study was small. In the further research, we need to recruit more to verify our positive findings. Second, we used SPT instead of conjunctival provocation test which is an established diagnostic procedure for allergic conjunctivitis. Because the conjunctival provocation test is not usually used in the clinic regarding the relative risks for children . SPT has higher accuracy in the diagnosis compared with serum-specific IgE in vitro[2, 25]. Even so, conjunctival provocation test, serum-specific IgE or SPT can only be considered as a diagnostic tool for evaluation the allergic status of individuals, but not to a diagnosis tool. Third, since our subjects were too young to accomplish such a questionnaire adequately, all the questionnaires were answered by their parents. But even parents can have limited understanding of subjects’ routines. Last but not the least, our results showed all subjects in the control group were negative to the SPT test considering dust mite allergen, allergic conjunctivitis patients more frequently displayed allergic reactions to it. It suggested that allergic background made subjects more sensitive to dust mite allergen rather than dust mite causing seasonal and perennial allergic conjunctivitis.